Plant Root Secretions and Their Interactions with Neighbors.- Root Exudates of Legume Plants and Their Involvement in Interactions with Rhizobia.- Flavonoids and Strigolactones in Root Exudates as Signals in Root-Fungus Interactions.- Plant Volatiles - Synthesis, Emission, Function.- Ligno-Cellulose Decomposition by Microbial Secretions.- Proteoid Roots and Exudation of Proteases by Plant Roots.- Unity is Strength: The Power of Border Cells and Border-like Cells in Relation with Plant Defence.- Sugary Exudates in Plant Pollination.- Nectar Secretion: its Ecological Context and Physiological Regulation.- Secretions in the Diatoms.- Microbial Quorum Sensing.- Inter-Organ and -Tissue Communication via Secreted Proteins.